Hi Dani,
At this time, only our formula text fields allow HTML tags. You can use a formula text field to display the value in your multiple choice field, though. The following link as well as this article explains the steps.
Color the Background of a Field with HTML
https://www.quickbase.com/help/color_field.html
If you get stuck, please enter a support case and we'll help you out!
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1. Log in to QuickBase at www.quickbase.com.
2. Go to http://support.quickbase.com and select "Enter a support case."
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From here you can see your previous and current cases.
Thanks!
Karis
QuickBase Support

This is great. I just needed the cell colored so I went with the following formula:
If([Summary VVL Fac]>0," "," ")
I found that (at least in Firefox) the pixel width needed to be specified with the number and "px" (width:40px).